1. Field of the Invention
The present invention pertains to devices for cleaning the inner walls of well casings, liners and similar conduits, and more particularly, to casing scrapers capable of scraping a film or cake of cement, mud, parafin, gun shot burrs, or any type of scaly materials, from the inner wall of such conduits.
2. Discussion of the Prior Art
Devices are known for scraping substances of the character mentioned above from the inner walls of well conduits; see, for example, the following patents listed below:
U.S. Pat. No. 1,664,283, Boynton PA0 U.S. Pat. No. 2,275,939, Baker PA0 U.S. Pat. No. 2,515,149, Willhoit PA0 U.S. Pat. No. 2,667,930, Saurenman PA0 U.S. Pat. No. 2,667,931, Baker PA0 U.S. Pat. No. 2,695,673, Coyle PA0 U.S. Pat. No. 2,804,152, Scivally PA0 U.S. Pat. No. 2,811,210, Guillot PA0 U.S. Pat. No. 2,838,121, Coyle PA0 U.S. Pat. No. 2,845,129, Baker PA0 U.S. Pat. No. 3,326,294, Neilson PA0 U.S. Pat. No. 3,276,521, Turbyfill PA0 U.S. Pat. No. 4,189,000, Best PA0 U.S. Pat. No. Re. 24,766 Scivally.
Needless to say, the prior art is very highly developed, and because of the relatively massive character of the casing scraper involved, and the great depths at which it is raised and lowered within a well casing, for example, considerable torques and stresses are placed on the tool during its operation in the well casing.
Tools of the character involved have been provided with reversely directed blades, i.e., sets of blades which have reversed pitches so that the scraper is operative both on descent and ascent within the well casing; see, for example, the U.S. Pat. No. 1,664,283, to Boynton; the U.S. Pat. No. 2,515,149, to Willhoit; Saurenman, U.S. Pat. No. 2,667,930; or Coyle, U.S. Pat. No. 2,695,673.
A scraper tool must be readily manufactured and assembled, be of a construction to withstand the wear to which it is subjected, and the scraper blades per se should be readily replaceable. The prior art submitted above is the closest prior art of which the applicant is aware; however, the citation of this art should not be construed as a representation that no better art exists or that a search has been made.